Michael Crichton has not been diagnosed with MS.
He had a single neurological episode in the 1960s and has not
had any other symptoms subsequently.

Ozzy Osbourne had a scare that he might have MS but it was a false alarm:
"Family unity became even more paramount for the Osbournes in 1992 when Ozzy
was diagnosed as suffering from multiple sclerosis, announced his retirement
and played a farewell tour. Six months later a second opinion pronounced the
diagnosis a false alarm, but the family have only now publicly acknowledged
the scare." - from this
Guardian article

There is also some dispute as to whether Dino Ferrari of Ferrari automobiles had MS.